Method of updating channel information by a mobile station that is in power saving mode

ABSTRACT

A method of updating channel information by a mobile station (MS) that is in power saving mode is disclosed. More specifically, the method includes the MS which receives status information of a first channel descriptor and transmission frame information which includes when the first channel descriptor is to be transmitted. Furthermore, the MS compares status information of the first channel descriptor with status information of a second channel descriptor. Here, the second channel descriptor is stored in the MS. Lastly, if the compared status information are different, the MS receives the first channel descriptor according to the transmission frame information.

This application is a continuation of U.S. application Ser. No.11/325,871, filed Dec. 30, 2005, currently pending, which claims thebenefit of Korean Application Nos. 10-2004-0117275 filed on Dec. 30,2004, 10-2005-0019841 filed on Mar. 9, 2005, and 10-2005-0131043 filedon Dec. 27, 2005, which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of updating channelinformation, and more particularly, to a method of updating channelinformation by a mobile station that is in power saving mode.

2. Discussion of the Related Art

In a Broadband Wireless Access System, an operation of a power savingmode is as follows. A paging zone refers to all the paging areas coveredby a plurality of base stations. Here, all the base stations in the samepaging zone share a same paging cycle (i.e., Paging_Cycle) and a samepaging offset (i.e., Paging_Offset).

In the system, a mobile station (MS) can request to enter a power savingmode from the base station (BS). The BS can then permit the MS to enterthe power saving mode by transmitting its paging group identification(i.e, Paging_Group_ID) and the paging cycle and the paging offset, bothcorresponding to the paging group ID. Upon receiving the paging groupID, the corresponding paging cycle, and the corresponding paging offset,the MS can then enter the power saving mode.

During the power saving mode, the MS receives a broadcast message in aform of a paging broadcast message (i.e., MOB-PAG-ADV) from the BS atspecified paging cycle. From the paging broadcast message, the MS candetermine whether to maintain or terminate the power saving mode.

If a situation arises where the MS has to send uplink traffic to the BS,the MS can terminate the power saving mode anytime. Conversely, if asituation arises where the MS, which is in the power saving mode, has toreceive downlink traffic from the BS, the BS sends the paging broadcastmessage to instruct the MS to terminate the power saving mode.

Alternatively, if the MS, which is in a power saving mode fails toreceive the paging broadcast message at the specified time as a resultof moving to another paging zone or by failure to synchronize, then theMS has to terminate the power saving mode.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method of updatingchannel information by a mobile station that is in power saving modethat substantially obviates one or more problems due to limitations anddisadvantages of the related art.

An object of the present invention is to provide a method of updatingchannel information by a mobile station that is in power saving mode.

Another object of the present invention is to provide a method ofproviding channel information by a base station to a mobile station thatis in power saving mode.

A further object of the present invention is to provide an apparatus forupdating channel information by a mobile station that is in power savingmode.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod of updating channel information by a mobile station (MS) that isin power saving mode includes the MS which receives status informationof a first channel descriptor and a transmission frame information whichincludes when the first channel descriptor is to be transmitted.Furthermore, the MS compares status information of the first channeldescriptor with status information of a second channel descriptor. Here,the second channel descriptor is stored in the MS. Lastly, if thecompared status information are different, the MS receives the firstchannel descriptor according to the transmission frame information.

In another aspect of the present invention, a method of providingchannel information by a base station (BS) to a mobile station (MS) thatis in power saving mode, includes the BS which transmits statusinformation of a first channel descriptor and transmission frameinformation which includes when the first channel descriptor is to betransmitted. Moreover, the BS transmits the first channel descriptoraccording to the transmission frame information.

Yet, in another aspect of the present invention, an apparatus forupdating channel information by a mobile station (MS) that is in powersaving mode includes a receiver for receiving status information of afirst channel descriptor and a transmission frame information whichincludes when the first channel descriptor is to be transmitted. Inaddition, the apparatus includes a comparator for comparing statusinformation of the first channel descriptor with status information of asecond channel descriptor. Here, the second channel descriptor is storedin a memory of the MS. Lastly, the apparatus includes the receiver forreceiving the first channel descriptor according to the transmissionframe information, if the compared status information from thecomparator are different.

Another aspect of the present invention includes a method of updatingchannel information by a mobile station (MS) that is in power savingmode. In the method, the MS receives status information of a channeldescriptor and a transmission frame information which includes when thechannel descriptor is to be transmitted. Furthermore, the MS recognizesa change in the status information of the channel descriptor since alast decoded status information. Lastly, the MS receives the channeldescriptor according to the transmission frame information.

In another aspect of the present invention, a method of updating channelinformation by a mobile station (MS) that is in power saving modeincludes the MS which receives a transmission frame information whichincludes a specified frame at which a channel descriptor is to betransmitted. Moreover, the MS recognizes the specified frame forreceiving the channel descriptor which contains information differentfrom channel descriptor information stored in the MS. Lastly, the MSreceives the channel descriptor at the specified frame.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings;

FIG. 1 is a diagram illustrating an example of an operation of a powersaving mode according to updated status information of a DCD/UCD;

FIG. 2 illustrates an example of a transmission operation of a pagingbroadcast message or a common downlink notification DL-MAP IE;

FIG. 3 is a diagram illustrating an example of an operation of a DCD/UCDtransmission offset;

FIG. 4 illustrates is a diagram illustrating an example of a pagingcycle synchronized to a DCD/UCD transmission cycle;

FIG. 5 is a diagram illustrating an example of an initial rangingoperation by the MS according to coding scheme and modulation schemeschanges in the BS; and

FIG. 6 is diagram illustrating an example of an operation using a framenumber instead of a DCD/UCD transmission offset.

FIG. 7 is a diagram illustrating an example of an apparatus in a powersaving mode which updates channel information.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In connection with the present invention, a more detailed description ofa power saving mode as well as a Downlink Channel Descriptor (DCD) andan Uplink Channel Descriptor (UCD) is provided in an IEEE 802.16especification document.

As described above, the MS in a power saving mode receives a pagingbroadcast message (i.e., MOB_PAG_ADV), which is transmitted according toa paging cycle, from the BS in the paging zone. Here, the power savingmode can be an idle mode or a sleep mode.

Table 1 represents an example of a Paging-Group-Action message forforming a paging zone. Here, the base stations can transmit messagesbetween each other via a wired connection (e.g., a cable).

TABLE 1 Field Size Notes Paging-group-action Message Format( ){ MessageType  8 bits Sender BS-ID 48 bits Base station unique identifier(Samenumber as that broadcasted on the DL-MAP message) Target BS-ID 48 bitsBase station unique identifier(Same number as that broadcasted on theDL-MPA message) Time Stamp 32 bits Number of millisecond since midnightGMT (set to 0xffffffff on the DL-MAP message) Action  4 bits 0-Assigntarget BS to paging group 1-Remove target BS from paging group 2-Query(to which paging group target BS belongs?) 3-Information (to whichpaging group sender BS belongs?) Num Record  4 bits Number of paginggroup-ID records For(j=0; j<Num Record; j++){  Paging-group-ID 16 bitsPaging-group-ID  PAGING_CYCLE 16 bits Cycle in which the paging messagein transmitted within the paging group  PAGING_OFFSET  8 bits MSS PAGINGOFFSET parameter  } Security field TBD A mean to authenticate thismessage CRC field 32 bits IEEE CRC-32  }

The messages transmitted between the base stations can be used forfollowing four purposes based on the indication of action bits. That is,if an action field indicates that Action=0, then the message can includea command to assign a target BS to a specified paging group. Here, thetarget BS is the BS that receives the message from another BS. On thecontrary, if the action field indicates that Action=1, then the messagecan include a command to remove or exclude the target BS from aspecified paging group. Furthermore, if the action field indicates thatAction=2, then the message can include a query as to which paging groupthe target BS belongs. Lastly, if the action field indicates thatAction=3, then the message can include information as to which paginggroup a sender BS belongs. Here, the sender BS is the BS that transmitsthe message from another BS.

Because one BS can belong to more than one paging group, apaging-group-action message can include information on a plurality ofpaging groups. In addition, the base stations can gain access to thepaging cycle and the paging offset of each paging zone from thepaging-group-action, which is shared by base stations.

Table 2 is an example of a deregistration request message (i.e.,DREG_REQ), which is a message by the MS to request to enter a powersaving mode.

TABLE 2 Syntax Size Notes DREG-REQ_Message_Format( ){  ManagementMessage Type=29 8 bits 0x00 = SS de-registration request from BS andnetwork 0x01 = request for MS deregistration from Serving BS invitationof MS paging Availability Mode 0x02-0xFF = reserved  De-registrationRequest Code 8 bits Only valid if De- Registration Request Code = 0x01 Paging Cycle Request 16 bits   TLV encoded parameter variable  }

According to Table 2, the MS can set a De-Registration Request Code ofthe DREG_REQ message to ‘0×01,’ and request for deregistration from aserving BS. That is, the MS requests the BS for permission to enter apower saving mode. Here, the serving BS refers to the BS which sendspaging information to mobile stations in its coverage area. In addition,the MS can send its preferred paging cycle in the DREG_REQ message.

Table 3 is an example of a deregistration command message (i.e.,DREG_CMD).

TABLE 3 Syntax Size Notes DREG-REQ_Message_Format( ){  ManagementMessage Type=29 8 bits  Action Code 8 bits  TLV encoded parametervariable  }

Using an ‘Action Code’ of the DREG_CMD message, the BS can permit the MSto enter a power saving mode (e.g., Action Code=0×05), have the MSrequest again the request to enter a power saving mode (e.g., ActionCode=0×06), or have the MS wait (or cease the requests to enter thepower saving mode) until the BS transmits the DREG_CMD message (e.g.,Action Code=0×07).

Table 4 is an example of action codes of a deregistration command (i.e.,DREG_CMD) message.

TABLE 4 Action Code Action 0x00 SS shall leave the current channel andattempt to access another channel 0x01 SS shall listen to the currentchannel but shall not transmit until an RES- CMD message or DREG_CMDwith Action Code 0x00 is received 0x02 SS shall listen to the currentchannel but only transmit on the Basic, Primary Management and SecondaryManagement Connections. 0x03 SS shall return to normal operation and maytransmit on any of its active connections. 0x04 SS shall terminatecurrent Normal Operation with the BS; the BS shall transmit this actioncode only in response to any SS DREG-REQ 0x05 required MSSde-registration from Serving BS and request initiation of MSS Idle Mode0x06 The MSS may retransmit the DREG-REQ message after the time duration(REQ-duration) given by 0x07 The MSS shall not retransmit the DREG-REQmessage and shall wait the DREG_CMD message 0x08-0xFF Reserved

By using a type-length-field (TLV) parameters, which can be selectivelyincluded in the DREG_CMD message, a paging group ID, a paging cycle, anda paging offset can be transmitted to the MS. The paging group ID, thepaging cycle, and the paging offset must be kept (unchanged) while thecorresponding MS is in the power saving mode. After the MS enters thepower saving mode, the MS receives a paging broadcast (i.e.,MOB-PAG-ADV) message at specified paging cycle(s) and at specifiedpaging offset. Based on the paging broadcast message, the MS can remainin or terminate the power saving mode.

Table 5 represents an example of a paging broadcast (i.e., MOB-PAG-ADV)message.

TABLE 5 Syntax Size Notes MOB_PAG-ADV_Message_Format( ){  ManagementMessage Type =62 8 bits  Num_Paging Group IDs 8 bits Number of PagingGroup IDs in this message  For(i=0; i<Num_Paging_Group_IDs; i++){  Paging Group ID 8 bits  }  For(j=0; j<Num_MACs; j++){ Number of MSSMAC Addresses in message can be determined from the length of themessage(found in the generic   MSS MAC Address hash 24 bits    ActionCode 2 bits Paging action instruction to MSS 00 = No Action Required 01= Performing Ranging to establish location and acknowledge message 10 =Enter Network 11 = reserved   Reserved 6 bits   }

In the Broadband Wireless Access System, the MS has to receive aDownlink Channel Descriptor/Uplink Channel Descriptor (DCD/UCD) fornetwork entry when the MS turns on power and for network re-entry inperforming operations such as handover.

Table 6 is an example of a Downlink Channel Descriptor (DCD).

TABLE 6 Syntax Size Notes DCD_Manage_Format( ){  Management MessageType=1 8 bits  Downlink Channel ID 8 bits  Configuration Change Count 8bits  TLV Encoded information for the variable TLV specific  overallchannel  Begin PHY Specification Section{   for(i=1; i<=n; i++){ Foreach downlink burst profile 1 to n    Downlink_Burst_Profile PHYspecific    }   }  }

Table 7 is an example of an Uplink Channel Descriptor (UCD).

TABLE 7 Syntax Size Notes UCD_Manage_Format( ){  Management MessageType=0 8 bits  Configuration Change Count 8 bits  Ranging Backoff Start8 bits  Ranging Backoff End  Ranging Backoff Start  Ranging Backoff End TLV Encoded information for the variable TLV specific  overall channel Begin PHY Specification Section{   for(i=1; i<=n; i++){ For eachdownlink burst profile 1 to n    Uplink_Burst_Profile PHY specific    }  }  }

The DCD/UCD messages are physical layers parameters which apply to eachallocated burst intervals for downlink and uplink. Moreover, the DCD/UCDmessages include information on a modulation scheme and a Forward ErrorCorrection (FEC) code type. Furthermore, using the DCD/UCD messages,necessary parameters (e.g., K and R values of a RS code) are providedaccording to various FEC code types. These types of parameters can beprovided via Burst Profile. Here, the Burst Profile is provided for eachUplink Interval Usage Code (UIUC) and Downlink Interval Usage Code(DIUC) from the UCD and the DCD.

The status information or the parameters and setting that can beincluded in the DCD/UCD messages can vary depending on the physicallayers. As such, the parameters or settings provided in Tables 8 and 9can be included in a ‘TLV Encoded Information for the overall channel’field of each message.

Table 8 is an example of parameters included in a ‘TLV EncodedInformation for the overall channel’ field of the DCD message in anOrthogonal Frequency Division Multiple Access (OFDMA).

TABLE 8 Type Value PHY Name (byte) Length (variable length) scopeDownlink_Burst_Profile 1 May appear more once. The length is the numberAll of bytes in the overall object, including embedded TLV items BSEIRPS 2 2 Signed in units of 1 dBM All Frame 3 4 The number of PSscontained in a Burst FDD or SC Duration TDD frame. Required only forframe downlinks PHY Type 4 1 The PHY Type to be used SC Power 5 1 0 =Preserve Peak Power SC, SCa adjustment 1 = Preserve Mean Power ruleDescribe the power adjustment rule when performing a transition from oneburst profile to another. Channel 6 1 Downlink channel number as definedin 8.5. Used SCa, Number for license-exempt operation only. OFDM, OFDMATTG 7 1 TTG (in PSs) SCa, OFDM, OFDMA RTG 8 1 RTG (in PSs) SCa, OFDM,OFDM, OFDMA RSS_(IR)_max 9 2 Initial Ranging Max. Received SignalStrength at All BS Signal in units of 1 dBm Channel 10 3 Channel switchframe number as defined in 6.3. SCa, Switch 15.7, Used forlisense-exempt operation only OFDM, Frame OFDMA Number Frequency 12 4Downlink center frequency(kHz) All BS ID 13 6 Base Station ID SCa, OFDM,OFDMA Frame 14 1 The duration of the frame. The frame duration OFDMDuration code values are specified in Table 230. Code Frame 15 3 Thenumber of the frame containing the DCD OFDM Number message.

Table 9 is an example of settings or parameters included in a ‘TLVEncoded Information for the overall channel’ field of the UCD message inan Orthogonal Frequency Division Multiple Access (OFDMA).

TABLE 9 Type Name (byte) Length Value Initial ranging 150 1 Number ofinitial ranging CDMA codes. Possible codes values are 0-225. Periodicranging 151 1 Number of periodic ranging CDMA codes. Possible codesvalues are 0-225. Bandwidth 152 1 Number of bandwidth request codes.Possible values request codes are 0-225. Periodic ranging 153 1 Initialbackoff window size for periodic ranging backoff start contention,expressed as a power of 2. Range: 0-15 (the highest order bits shall beunused and set to 0). Periodic ranging 154 1 Final backoff window sizefor periodic ranging backoff end contention, expressed as a power of 2.(the highest order bits shall be unused and set to 0). Start of ranging155 1 Indicates the starting number, S, of the group of codes codesgroup used for this uplink. All the ranging codes used on this uplinkwill be between S and ((S + N + M + L)mod256). Where, N is the number ofinitial-ranging codes M is the number of periodic-ranging codes L is thenumber of bandwidth-request codes M is the number of periodic-rangingcodes L is the number of bandwidth-request codes The range of value is 0≦ S ≦ 255 Permutation base 156 1 Determine the UL_IDcell parameter forthe subcarrier permutation to be used on this uplink channel. ULallocated 157 9 This is a bitmap describing the sub-channels allocatedsub-channels to the segment in the UL, when using uplink PUSC bitmappermutation. The LSB of the first byte shall correspond to subchannel 0.For amy bit that is not set, the corresponding subchannel shall not beused by the SS on that segment.

In the system, the DCD/UCD messages are not limited to settings orparameters contained in Tables 8 and 9. In other words, the DCD/UCDmessages can include other information besides the information listed inTables 8 and 9.

As shown in Table 6-Table 9, the DCD/UCD message contains large volumesof information. As such, it would be inefficient for the MS to decodeevery DCD/UCD messages received. Furthermore, the DCD/UCD message ofTables 6 and 7 includes Configuration Change Count parameter. Here, theConfiguration Change Counter can increase by increments of one (I) ifthe value(s) contained in the current DCD/UCD message is (are) differentfrom the value(s) contained in a previous DCD/UCD message. In otherwords, if the MS recognizes that there is change in status informationof a received DCC/UCD from status information of the DCD/UCD stored inthe MS, then the Configuration Change Counter increases by a specifiedincrement. The settings or parameters can also be referred to as statusinformation.

As discussed above, lengths of the DCD/UCD messages are not only longbut information contained in the DCD/UCD messages are relativelyconstant. That is, the DCD/UCD messages generally do not change often.Therefore, the DCD/UCD messages are not transmitted in every frame, andmore realistically, the DCD/UCD messages are transmitted periodicallywith a maximum period of 10 seconds, for example.

As for the BS, the BS transmits the DCD/UCD message containing a newstatus information (or new values) after waiting a specified time periodso that all mobile stations in its cell coverage area can receive theDCD/UCD message. Here, the Configuration Change Counter included in theDCD/UCD message increases by an increment of 1). Thereafter, the BSapplies the updated or changed status information of the DCD/UCD to theburst profile of the uplink/downlink frame(s).

As shown in Table 10 and Table 11, the updated status information can beprovided to the MS by using a DL-MAP message and a ‘DCD/UCD Count’ fieldincluded in an UL-MAP message. Since the DL-MAP message and the UL-MAPmessage are encoded with predefined values of the physical layer, the MScan decode the changed status information in the DCD message and the UCDmessage.

Table 10 is an example of a DL-MAP.

TABLE 10 Syntax Size Notes DL-MAP_Message_Format( ){  Management MessageType=2 8 bits  PHY Synchronization Field variable See appropriate PHYspecification  DCD Count 8 bits  Base Station ID 48 bits   Begin PHYSpecific Section { See applicable PHY section   for(i=1; j<=n; i++){ Foreach DL-MAP element 1 to n    DL-MAP_IE( ) variable See correspondingPHY specification    }   }  if!(byte boundary){   Padding Nibble 4 bitsPadding to reach byte boundary  }  }

Table 11 is an example of an UL-MAP.

TABLE 11 Syntax Size Notes UL-MAP_Message_Format( ){  Management MessageType=3 8 bits  Uplink Channel ID 8 bits  UCD Count 8 bits  AllocationStart Time 32 bits   Begin PHY Specific Section{ See applicable PHYsection   for(i=1, i<=n, i++) { For each US-MAP element 1 to n   UL-MAP_IE( ) variable See corresponding PHY specification   } Paddingto reach byte boundary   }  if!(byte boundary){  Padding Nibble  }  }

After the MS receives an updated DL-MAP/UL-MAP having status informationdifferent from that of the previous status information, the MS uses thestatus information (or values) included in the last received DCD/UCDmessage to decode the bursts included in the correspondingDL-MAP/UL-MAP.

FIG. 1 is a diagram illustrating an example of an operation of a powersaving mode according to updated status information of a DCD/UCD.

If the paging broadcast message is configured to be transmitted using apredetermined coding and modulation schemes, then the MS in the powersaving mode can still receive the paging broadcast message even if noDCD/UCD message is received.

However, if the predetermined coding and modulation schemes are notused, the MS in the power saving mode does not receive a DCD/UCDmessage, and the BS changes (or updates) the coding and modulationschemes, the MS has to terminate the power saving mode since the MS isunable to decode the paging broadcast message. Alternatively, if the MSbelongs to the same paging group but moves to a cell using differentcoding and modulation schemes, the MS has to terminate the power savingmode since the MS cannot decode the paging broadcast message.Alternatively, if the MS in the power saving mode does not receive anyDCD/UCD messages, the re-entry to the network by the MS can takeadditional time since the MS has to receive the DCD/UCD message in orderto receive the current coding and modulation schemes. As such, it seemsnecessary and practical for the MS in the power saving mode to be ableto receive the DCD/UCD messages.

If the MS is configured to receive the DCD/UCD messages while in thepower saving mode, the MS in the power saving mode can decode thedownlink frame during a specified cycle. Furthermore, if the DCD/UCDstatus information (or values) are updated or changed during a PagingUnavailable Interval or if the MS has moved to another cell within thesame paging group, the MS has to continuously receive and decode allsubsequent downlink frames until the new DCD/UCD message with updated orchanged status information is received. Here, the Paging UnavailableInterval is an interval or a period in which the MS does not receive anddecode any downlink frames in order to conserve power. Moreover, asdiscussed above, the DCD/UCD message contains a Configuration ChangeCounter which is independently managed by each BS. For example, a firstBS and a second BS belong to the same paging group. However, since theConfiguration Change Counters independent of each other BS, the Counterof the first BS could be indicating 2 while the Counter of the second BScould be indicating 5. In addition, since the transmission cycle of theDCD/UCD message can be long (e.g., up to 10 seconds per cycle), thepower consumption of the MS in the power saving mode can be significant.

Table 12 is an example of a paging broadcast message (i.e.,MOB-PAG-ADV).

TABLE 12 Syntax Size Notes MOB_PAG-ADV_Message_Format( ){  ManagementMessage Type =??  8 bits  Num_Paging Group IDs  8 bits Number of PagingGroup IDs in this message  For(i=0; i<Num_Paging_Group_IDs; i++){  Paging Group ID  8 bits   }  For(j=0; j<Num_MACs; j++){   MSS MACAddress hash 24 bits   Action Code  2 bits Paging action instruction toMSS 00 = No Action Required 01 = Perform Ranging to establish locationand acknowledge message 10 = Enter Network 11 = reserved   Reserved  6bits   } DCD Transmission Indicator  1 bit Indicates whether DCD messageis included in the next Paging Unavailable Interval or not. 0 = Notincluded 1 = Included DCD Transmission Indicator  1 bit Indicateswhether UCD message is included in the next Paging Unavailable Intervalor not. 0 = Not included 1 = Included TLV Encoded Information variableTLV Specific Reserved Padding bits to ensure octet aligned.  }

The paging broadcast message of Table 12 is different from the pagingbroadcast message of Table 5 in that the paging broadcast message ofTable 12 includes a DCD/UCD Transmission Indication to determine whethertransmission of the DCD/UCD message is scheduled during the PagingUnavailable Interval.

If the DCD/UCD Transmission Indication is set at ‘1,’ a DCD/UCDTransmission Offset can be provided in a form of TLV in the pagingbroadcast message, as shown in Table 13.

TABLE 13 Name Type Length Value DCD/UCD TBD 16 bits This value may beincluded in MOB_PAG-ADV Transmission offset message when DCDTransmission Indication in the message is set to 1, and indicates thenumber of frames left for the next transmission of DCD message. UCDTransmission TBD 16 bits This value may be included in MOB_PAG- offsetADV message when UCD Transmission Indication in the message is set to 1,and indicates the number of frames left for the next transmission of UCDmessage.

The DCD/UCD Transmission Indication of the paging broadcasts message ofTable 12 and the DCD/UCD Transmission Offset of Table 13 can be in aform of a common downlink notification information element (i.e.,Common_DL_Notification_IE) DL-MAP message as provided in Table 14. Thecommon downlink notification information element can be included in aDL-MAP IE which is transmitted during the paging cycle. The DCD/UCDtransmission offset bitmap is used to identify whether the offset is forthe DCD or UCD.

Table 14 is an example of a common downlink notification DL-MAP message.

TABLE 14 Syntax Size Notes Common_DL_Notification_IE( ){  Extended UIUC 4 bits  Length  4 bits Length in Bytes  DCD Transmission Indication  1bit Indicates if DCD message is included in the next Paging UnavailableInterval or not. 0 = Not included 1 = Included  UCD TransmissionIndication  1 bit Indicates if UCD message is included in the nextPaging Unavailable Interval or not. 0 = Not included 1 = Included DCD/UCD Transmission offset bitmap  2 bits This bitmap indicates; 00:No DCD/UCD offset is included. 01: DCD offset is included. 10: UCDoffset is included. 11: DCD/UCD offsets are included.  reserved  4 bitsPadding for byte alignment  DCD Transmission offset 16 bits This valuemay be included when DCD Transmission Indication set to 1, and indicatesthe number of frames left for the next transmission of DCD message.  UCDTransmission offset 16 bits This value may be included when UCDTransmission Indication set to 1, and indicates the number of framesleft for the next transmission of UCD message.  }

FIG. 2 illustrates an example of a transmission operation of a pagingbroadcast message of Table 12 or a common downlink notification DL-MAPIE of Table 14. Referring to FIG. 2, the MS that is in the power savingmode identifies a change in the Configuration Change Counter included inthe DCD/UCD message from the paging broadcast message received duringthe paging listening interval. Once the change is identified, the MSthat is in the power saving mode has to obtain the DCD/UCD transmissionindication parameters of the paging broadcast message which is receivedduring the paging listening interval.

If the DCD/UCD transmission identification parameter is ‘0,’ the MSknows that no DCD/UCD message transmitted during the next pagingunavailable interval. Then the MS maintains normal power saving modeinstead of waiting to receive the UCD/DCD message until the next paginglistening interval.

On the contrary, the DCD/UCD transmission identification parameter setto ‘1’ signifies that the DCD/UCD message is to be transmitted duringthe next paging unavailable interval. As such, the MS does not return topaging unavailable interval even after expiration of the listeninginterval until the MS receives the DCD/UCD message. In other words, theMS stays awake (maintains listening interval) until the DCD/UCD messageis received. Upon receipt, the MS returns to the paging unavailableinterval.

FIG. 3 is a diagram illustrating an example of an operation of a DCD/UCDtransmission offset of Tables 13 and 14. In FIG. 3, the paging broadcastmessage can indicate an exact time (or frame) of when the DCD/UCDmessage is to be included in the transmission of the paging broadcastmessage. Therefore, the corresponding mobile stations can receive theDCD/UCD messages during the paging unavailable interval.

As another embodiment of the present invention, a DCD/UCD transmissionoffset can be used, instead of the DCD/UCD transmission indication toindicate whether the DCD/UCD message is transmitted during the pagingunavailable interval. Here, the DCD/UCD transmission indication of Table12 is removed or not used in the paging broadcast message. However, ifthe situation calls for the BS to transmit a DCD/UCD message during thepaging unavailable interval, the DCD/UCD transmission offset TLVparameter can be included in the paging broadcast message, and the MSstays awake or enter paging unavailable interval until the pagingbroadcast message containing the DCD/UCD message is received, even afterexpiration of the listening interval. Alternatively, if the BS does nottransmit the DCD/UCD message during the next paging unavailableinterval, the DCD/UCD transmission offset TLV parameter is not includedin the paging broadcast message. After the MS receives this pagingbroadcast message absent the DCD/UCD transmission offset TLV parameterand recognizes that the DCD/UCD message is not expected to betransmitted during the next paging unavailable interval. Therefore, theMS maintains normal power saving operation mode without staying awake.

FIG. 4 is a diagram illustrating an example of a paging cyclesynchronized to a DCD/UCD transmission cycle. As illustrated in FIG. 4,if the paging cycle of the power saving mode and the DCD/UCD messagetransmission cycle (i.e., DCD/UCD interval) are synchronized, all mobilestations in the paging listening interval of the power saving mode canreceive the DCD/UCD messages during every paging listening interval. Assuch, the features of the embodiments of the present invention can berealized without the proposed operations presented in the embodiments ofthe present invention.

FIG. 5 is a diagram illustrating an example of an initial rangingoperation by the MS according to coding scheme and modulation schemeschanges in the BS. First, to perform initial ranging operation, theDCD/UCD message has to be received by the MS. Thereafter, if the MS isdirected to perform initial ranging operation, then the BS can transmitthe DCD/UCD message to the MS that is in the power saving mode.

After the MS receives the ranging request message via the pagingbroadcast message, the MS performs following ranging operation. First,the MS receives the DCD/UCD message, followed by transmitting a rangingrequest (i.e., RNG-REQ) message, and thereafter receives a rangingresponse (i.e., RNG-RSP) message. After the ranging response message isreceived, the MS maintains the power saving mode. That is, if the MSreceives and successfully decodes the DCD message and the UCD messageand also receives the ranging response message, then the MS enters thepaging unavailable interval to maintain the power saving mode.

FIG. 6 is diagram illustrating an example of an operation using a framenumber instead of the DCD/UCD transmission offset of Table 14. If theDCD/UCD transmission offset is used, the transmission offset has to be16 bits considering a 16-bit maximum paging cycle of the power savingmode and a 10-second maximum DCD/UCD transmission cycle (e.g., 2000frames where 1 frame=5milliseconds). As for using the frame number, evenif lower 8 bits are used, a frame to transmit the DCD/UCD can beindicated, thus able to decrease the size of the transmission message.

If the frame number is used instead of the DCD/UCD transmission offset,information listed in Table 15 can be additionally included to thepaging broadcast message of Table 5 in a TLV format. Table 15 is anexample of using a frame number in a TLV format in the paging broadcastmessage.

TABLE 15 Name Type Length Value DCD/UCD TBD 8 bits This value may beincluded in MOB_PAG-ADV Transmission frame message when DCD TransmissionIndication in the message is set to 1, and indicates the leastsignificant eight bits of the frame number of the next DCD transmission.UCD Transmission TBD 8 bits This value may be included in MOB_PAG-ADVframe message when UCD Transmission Indication in the message is set to1, indicates the least significant eight bits of the frame number of thenext UCD transmission.

As described above, if the frame number is used instead of the DCD/UCDtransmission offset, Table 16 illustrates another example of the commondownlink notification (i.e., Common_DL_Notification_IE) DL-MAP IE to theexample of Table 14.

TABLE 16 Syntax Size Notes Common_DL_Notification_IE( ){  Extended UIUC4 bits  Length 4 bits Length of Bytes  DCD Transmission Indication 1 bitIndicates if DCD message is included in the next Paging UnavailableInterval or not. 0 = Not included 1 = Included  UCD TransmissionIndication 1 bit Indicates if UCD message is included in the next PagingUnavailable Interval or not. 0 = Not included 1 = Included  DCD/UCDTransmission offset 2 bits This bitmap indicates; bitmap 00: No DCD/UCDoffset is included. 01: DCD offset is included. 10: UCD offset isincluded. 11: DCD/UCD offsets are included.  reserved 4 bits Padding forbyte alignment  DCD Transmission frame 8 bits This value may be includedwhen DCD Transmission Indication in the message is set to 1, andindicates the least significant eight bits of the frame number of thenext DCD transmission.  UCD Transmission frame 8 bits This value may beincluded when UCD Transmission Indication in the message is set to 1,indicates the least significant eight bits of the frame number of thenext UCD transmission.  }

Table 17 is an example of a Broadcasts Control Pointer IE included inthe DL-MAP message if the frame number is used instead of the DCD/UCDtransmission offset.

TABLE 17 Syntax Size Notes Broadcast Control Pointer IE( ){  ExtendedUIUC 4 bits 0x0A  Length 4 bits Length of Bytes  DCD_UCD Configuration 4bits A composite configuration  Change Counter change counterincremented for each change in either DCD or UCD.  DCD_UCD Transmission8 bits The least significant eight bits  Frame of the frame number ofthe next DCD and/or UCD transmission  reserved 4 bits Shall be set tozero }

If a DCD_UCD Configuration Change Counter setting or parameter of theBroadcast Control Pointer IE of Table 17 is different from a DCD_UCDConfiguration Change Counter setting or parameter stored in the MS, theMS receives and decodes the DCD/UCD message transmitted from the BS evenafter the MS has entered the paging unavailable interval. Here, theDCD/UCD message can be received by synchronizing the downlink frame withthe transmission frame indicated in the Broadcast Control Pointer IE.That is, the MS awakes up or exits the paging unavailable intervalduring the frame. After the UCD/DCD messages are received, the MSreturns to or enters the paging unavailable interval for maintaining thepower saving mode.

However, if the MS fails to successfully decode the DCD/UCD message andif the BS does not transmit the DCD message or the UCD message at thespecified transmission frame, the MS has to receive and decode allsubsequent downlink frames to receive the DCD message or the UCD messagewith updated or changed status information or parameters. After theUCD/DCD messages are received, the MS returns to or enters the pagingunavailable interval for maintaining the power saving mode.

As illustrated in FIG. 6, if the DCD/UCD message is scheduled to betransmitted during the next paging unavailable interval (e.g., at frameA), the BS can transmit information which includes that the message isto be transmitted via either the paging broadcast message, the DCD/UCDtransmission indication of the common downlink notification DL-MAP IE,or the DCD/UCD transmission offset bitmap during the next pagingunavailable interval.

Furthermore, the BS can indicate the lower 8 bits of the frame number,through which actual transmission is to take place, using the DCDtransmission frame and the UCD transmission frame. Using this scheme,the MS can receive the DCD/UCD message transmitted to the correspondingframe even during the paging unavailable interval.

As indicated in Table 14 and Table 16, the DCD transmission indication,the UCD transmission indication, and the DCD/UCD transmission offsetbitmap has a length of 1 bit, 1 bit, and 2 bits, respectively. Here,information contained in the DCD transmission indication, the UCDtransmission indication, and the DCD/UCD transmission offset bitmap canbe represented by using a flag, which has a length of 2 bits.

Table 18 is an example illustrating a flag.

TABLE 18 DCD/UCD 2 bits For each bit location, a value of indicatestransmission that DCD and UCD transmission is indication flag scheduledduring next Paging Unavailable Interval. Bit 0: DCD transmission duringnext Paging Unavailable Interval. UCD transmission is scheduled duringnext Paging Unavailable Interval. Bit 0: DCD transmission during nextPaging Unavailable Interval. Bit 1: UCD transmission during next PagingUnavailable Interval.

As shown in Table 18, a flag can be used to indicate whether the DCD/UCDis scheduled during the paging unavailable interval. For example, if theflag value or parameter is ‘00,’ this indicates that there is no DCD/UCDtransmission scheduled during the next paging unavailable interval. Ifthe parameter of the flag is ‘01,’ this indicates that only the DCD isscheduled for transmission. Moreover, if the flag parameter is ‘10,’this indicates that only the UCD is scheduled for transmission. Lastly,if the flag parameter is ‘11,’ then this indicates that both the DCD andthe UCD is scheduled for transmission.

In another embodiment of the present invention, an operation of updatingchannel information can be performed by an apparatus in a power savingmode. FIG. 7 is an example of an apparatus in a power saving mode whichis used to update channel information. In FIG. 7, the apparatus includesa receiver 10 which receives status information, such as the DCD messageand/or the UCD message, of a first channel descriptor and transmissionframe information which includes when the first channel descriptor isscheduled to be transmitted. The apparatus further includes a comparator20 which is used to compare status information of the first channeldescriptor with status information of a second channel descriptor. Here,the second channel descriptor is stored in a memory 30 of the MS.Furthermore, the receiver 10 also receives the first channel descriptoraccording to the transmission frame information if the compared statusinformation from the comparator 20 are different.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method for updating channel information of a mobile station whichis in an idle mode, comprising: receiving an information element (IE)including a channel descriptor configuration change counter and atransmission frame field indicating a frame in which a channeldescriptor is transmitted; and receiving the channel descriptor in theframe indicated by the transmission frame field, when the channeldescriptor configuration change counter is changed since the mobilestation last decodes the information element (IE), wherein if thechannel descriptor is not transmitted from a base station in the fieldindicated by the transmission frame field, the mobile station continuesdecoding subsequently received frames until the channel descriptor issuccessfully received.
 2. The method according to claim 1, wherein themobile station maintains the idle mode before receiving the channeldescriptor.
 3. The method according to claim 1, further comprising:receiving indication information indicating whether channel descriptortransmission is scheduled to transmit the channel descriptor during anext paging unavailable interval.
 4. The method according to claim 3,wherein the paging unavailable interval is an interval during which themobile station in the idle mode cannot communicate with the basestation.
 5. The method according to claim 1, wherein the informationelement (IE) is received during a paging interval.
 6. The methodaccording to claim 5, wherein the paging interval is an interval duringwhich the mobile station in the idle mode communicates with the basestation.
 7. The method according to claim 1, wherein the channeldescriptor is either an uplink channel descriptor (UCD) or a downlinkchannel descriptor (DCD).
 8. The method according to claim 7, wherein atleast one of the uplink channel descriptor (UCD) and the downlinkchannel descriptor (DCD) is a broadcast message.
 9. The method accordingto claim 1, wherein the information element (IE) is a broadcast controlpointer information element.
 10. The method according to claim 1,wherein the transmission frame field is 8-bits in size and indicateswhen a next channel descriptor is transmitted.
 11. The method accordingto claim 1, wherein the channel descriptor is a broadcast message. 12.The method according to claim 1, wherein the transmission frame fieldindicates a frame number.
 13. A mobile station for updating channelinformation in an idle mode, comprising: a receiver for: receiving aninformation element (IE) including a channel descriptor configurationchange counter and a transmission frame field indicating a frame inwhich a channel descriptor is transmitted; and receiving the channeldescriptor in the frame indicated by the transmission frame field, whenthe channel descriptor configuration change counter is changed since themobile station last decodes the information element, wherein if thechannel descriptor is not transmitted from a base station in the fieldindicated by the transmission frame field, the mobile station continuesdecoding subsequently received frames until the channel descriptor issuccessfully received.
 14. The mobile station according to claim 13,wherein the receiver further receives indication information indicatingwhether channel descriptor transmission is scheduled to transmit thechannel descriptor during a next paging unavailable interval.
 15. Themobile station according to claim 14, wherein the paging unavailableinterval is an interval during which the mobile station in the idle modecannot communicate with a base station.
 16. The mobile station accordingto claim 13, wherein the information element (IE) is received during apaging interval.
 17. The mobile station according to claim 16, whereinthe paging interval is an interval during which the mobile station inthe idle mode communicates with a base station.
 18. The mobile stationaccording to claim 13, wherein the channel descriptor is either anuplink channel descriptor (UCD) or a downlink channel descriptor (DCD).19. The mobile station according to claim 13, wherein the informationelement (IE) is a broadcast control pointer information element.
 20. Themobile station according to claim 13, wherein the transmission framefield is 8-bits in size and indicates when a next channel descriptor istransmitted.